OpenMP: Handle tofrom with target enter/exit data

OpenMP: Handle tofrom with target enter/exit data

In 5.2, a map clause can be map-entering or map-exiting,
either containing 'tofrom'. The main reason for this is
permit 'map(x)' with 'omp target enter/exit data',
avoiding to specify 'to:/from:' explicitly. (OpenMP
defaults to 'tofrom'.)

gcc/c/ChangeLog:

	* c-parser.cc (c_parser_omp_target_enter_data,
	c_parser_omp_target_exit_data): Accept tofrom
	map-type modifier but use 'to' / 'from' internally.

gcc/cp/ChangeLog:

	* parser.cc (cp_parser_omp_target_enter_data,
	cp_parser_omp_target_exit_data): Accept tofrom
	map-type modifier but use 'to' / 'from' internally.

gcc/fortran/ChangeLog:

	* dump-parse-tree.cc (show_omp_namelist): For the map-type,
	also handle the always modifer and release/delete.
	* openmp.cc (resolve_omp_clauses): Accept tofrom
	map-type modifier for target enter/exit data,
	but use 'to' / 'from' internally.

libgomp/ChangeLog:

	* libgomp.texi (OpenMP 5.2): Mark target enter/exit data
	with fromto as implemented.

gcc/testsuite/ChangeLog:

	* c-c++-common/gomp/target-data-2.c: New test.
	* c-c++-common/gomp/target-data-3.c: New test.
	* gfortran.dg/gomp/target-data-1.f90: New test.
	* gfortran.dg/gomp/target-data-2.f90: New test.